const _ = require('lodash');
const fp = require('lodash/fp');

//数据  horsepower马力，dollar_value价格,in_stock库存
const cars =[
    { name: 'Ferrari FF', horsepower:660, dollar_value:700000, in_stock: true },
    { name: 'Spyker C12 Zagato', horsepower:650, dollar_value:648000, in_stock: false },
    { name: 'Jaguar XKR-S', horsepower:550, dollar_value:132000, in_stock: false },
    { name: 'Audi R8', horsepower:525, dollar_value:114200, in_stock: false },
    { name: 'Aston Martin One-77', horsepower:750, dollar_value:185000, in_stock: true },
    { name: 'Pagani Huayra', horsepower:700, dollar_value:130000, in_stock: false }
]


// 使用帮助函数_average重构averageDollarValue，使用函数组合的方式实现
let _average = function (xs) {
    return fp.reduce(fp.add, 0, xs) / xs.length
}// <-无须改动

//改动前
let averageDollarValue = function (cars){
    let dollar_values = fp.map(function(car){
        return car.dollar_value
    },cars)
    return _average(dollar_values)
}

// const trace = _.curry((tag, v) => {
//      console.log(tag, v) 
//     return v })
//改动后
let averageDollarValueL  = cars => {
   let dollar_values = _.map(cars,'dollar_value')
   const fn = fp.flowRight(_average,dollar_values);
   console.log(fn(cars));
}

console.log(averageDollarValueL(cars))